Method for treating the surfaces of vehicle bodies

ABSTRACT

A METHOD AND AN APPARATUS FOR TREATING THE SURFACES OF ARTICLES, AND ESPECIALLY FOR PAINTING AUTOMOBILE BODIES OR OTHER LARGE ELONGATED ARTICLES, ESSENTIALLY CONSISTING IN PASSING THE ARTICLES WHILE THEIR GREATER LENGTH EXTENDS IN A VERTICAL DIRECTION FIRST THROUGH A PRELIMINARY TREATING ZONE, ESPECIALLY A PAINTING ZONE. THE PRELIMINARY TREATMENT PREFERABLY COMPRISES AN ELECTROCHEMICAL DIPPING PROCESS AND THE PAINTING TREATMENT OF AN ELECTRIC DIPPING PROCESS ACCORDING TO THE ELECTROPHORETIC PRINCIPLE. THE DIP TANKS ARE MAKE OF SHAPE IN ACCORDANCE WITH THE VERTICAL POSITION OF THE ARTICLES TO BE TREATED WHICH, WHILE BEING LIFTED OUT OF THE TANKS, ARE PREFERABLY KEPT MOIST BY ADDITIONALLY SPRAYING THE TREATING LIQUIDS THEREON WHICH ARE ALSO CONTAINED IN THE RESPECTIVE TANKS UNDERNEATH.

H. DURR Dec. 12, 1972 METHOD FOR TREATING THE SURFACES OF VEHICLE aonnzs Filed July 20, 1970 2 Sheets-Sheet l r & 1 m) 0; m w J 4 n a a J y% B METHOD FOR TREATING THE SURFACES OF VEHICLE BODIES Filed July 20, 1970 2 Sheets-Sheet 2 w Fig. 5

United States Patent METHOD FOR TREATING THE SURFACES OF VEHICLE BODIES Heinz Diirr, Stuttgart-Feuerbach, Germany, assignor to Otto Diirr, Stuttgart-Zuffenhausen, Germany Filed July 20, 1970, Ser. No. 56,415 Claims priority, application Germany, July 30, 1969, P 19 38 589.8; June 24, 1970, P 20 31 125.5 Int. Cl. B44d 1/14; B05c 3/02 US. Cl. 117-49 11 Claims ABSTRACT OF THE DISCLOSURE A method and an apparatus for treating the surfaces of articles, and especially for painting automobile bodies or other large elongated articles, essentially consisting in passing the articles while their greater length extends in a vertical direction first through a preliminary treating zone, especially a painting zone. The preliminary treatment preferably comprises an electrochemical dipping process and the painting treatment of an electric dipping process according to the electrophoretic principle. The dip tanks are made of a shape in accordance with the vertical position of the articles to be treated which, while being lifted out of the tanks, are preferably kept moist by additionally spraying the treating liquids thereon which are also contained in the respective tanks underneath.

The present invention relates to a method and an apparatus for treating large elongated articles in dip tanks, and more particularly for painting automobile bodies including preliminary treatments thereof such as degreasing and phosphatising and a subsequent prime coating and top coating of these bodies or other articles with paint or enamel. These treatments generally require a large number of individual steps since between the different main treating processes it is necessary to carry out intermediate treatments such as flushing, cooling, drying or the like and since the individual treatments are usually carried out in a series of steps or stations.

The preliminary treatment such as degreasing or phosphatising is usually carried out by spraying, while the painting is carried out either by spraying or dip-coating. Thus, for example, a zinc phosphatising process which is carried out by spraying is followed by painting the articles by means of an electric dipping process (electro phoresis). Although such a manner of treatment has numerous advantages, it also has the considerable disadvantage that, even though in painting a car body by the dipping method the internal parts of the body forming cavities will be fully covered, these parts will not be fully acted upon in the preceding cleaning and phosphatising operations. For attaining a proper protection of a car body from corrosion, it is, however, especially of importance that its internal surfaces including those of cavities will also be properly treated. It is a well-known fact that the corrosion of a car body starts on those parts of its surfaces, for example, on the door sills, back reinforcements, etc., which cannot be reached at all or only incompletely when treated by a spraying process. The insides of these parts act like steam chambers in which the strong climatic variations to which an automobile is subjected exert themselves to their full extent. Tests which have been made by galvanizing the material, by spraying it on the inside with plastic or special paints or by subjecting it to a preliminary chemical wet process, the so-called slipperdip process in which the car body was dipped to a level above the door sills, but was sprayed above this level did not produce any considerable advantages. The further possibility of attaining a proper protection from corrosion ice by subjecting all individual parts of a car body before the assembly to degreasing and zinc phosphatising treatments requires considerable expense for the necessary apparatus and amount of work and entails the danger that the phosphatised surfaces may be soiled during the intermediate operations.

It is a principal object of the present invention to eliminate these disadvantages of the known processes and to treat the surfaces of a car body so that the danger of corrosion especially of such parts thereof will be avoided which in a spraying process are inaccessible or can only be reached with ditficulty.

Another object of the invention consists in preventing the surfaces of the article from drying during the treatment.

A further object of the invention consists in providing an apparatus which requires a relatively small space, is of a relatively simple construction, and may operate very efiiciently and economically.

For attaining these objects, the invention is based on the presumption that, while the application of the dipping method is desirable also for the preliminary treatments, this alone is not sufiicient but that additional operations are necessary so as to render such a treatment as economical or nearly as economical as the spraying method as previously applied.

The objections to applying the dipping method also for carrying out the preliminary treatment are based primarily upon the fact that since the individual treating stages of this method require a considerably greater length of time than those of the spraying method, the expense for the necessary apparatus is also higher and that since the operations require chemicals of a higher concentration, the consumption of chemicals is also higher than in the spraying method. Furthermore, there is the danger that residues of the chemicals which after the preliminary treatment remain in the pores of the material of a car body will lead to a subsequent corrosion. Since when applying the dipping method, the material of the baths must also have a considerably higher temperature than that required for spraying, the metal surfaces will dry off when removed from each bath which will prevent a proper paint coating.

An important feature of the present invention therefore consists in carrying out the dip method by conveying the car bodies or similar large elongated articles preferably through all stages of the pretreatment zone and also of the painting zone and a possible finishing zone, if required, in a position in which their greater length extends in a vertical direction. The preliminary treatment is then preferably carried out by the electro-chemical dipping method and the paint coating by the electric dipping method according to the electrophoretic principle. Although the painting operation is preferably carried out according to this principle, the invention is not limited thereto, but it is to be understood that other suitable methods may also be applied.

Especially insofar as the treatment of automobile bodies is concerned, the present invention produces the following advantages:

(1) The surfaces of the cavities of a car body may be properly degreased and phosphatised since the liquid of the bath will also reach those parts of the body which are inaccessible from the outside. The dip-phosphatising method generally also results in a considerably better adhesion of the paint and a better protection from corrosion than the spraying method.

(2) By dipping the car body in a vertical position into the treating baths so that either its front or rear part hangs downwardly, the treating liquids will run off considerably faster when it is lifted out of the baths. While in the previously conventional treatment of such bodies in which they were dipped in a horizontal position, the car body retained the bath liquid like a ladle and the liquid could therefore run oii only very slowly and required additional openings to be provided in the bottom part of the body which subsequently had to be closed again, the vertically suspended position of the car body enables the liquid to run off easily, quickly and completely from the inside of the body. It is therefore possible to increase the speed of lifting the car body out of the bath considerably, for example, to a speed which may be twice or three or more times as high as the speed which was previously required. Consequently, the danger will be considerably reduced that the hot solutions might dry out on the surfaces instead of dripping off when the car body is withdrawn from the bath.

(3) By dipping the car body into each bath in a vertical position rather than horizontally, the length of each dip tank as seen in the direction in which the car body is conveyed from one tank to the other may be reduced considerably in accordance with the smaller cross-sectional size of the body as compared with its length. The entire apparatus containing all of the required equipment may therefore also be made of a much shorter length and requires less floor space so that the costs of building such an apparatus and for its upkeep will also be considerably reduced.

(4) Since the exposed surface of the bath in each dip tank is much smaller, the losses in heat are reduced accordingly and the operation of the apparatus is also for this reason more economical.

(5) Finally, the present invention permits the auxiliary means which are in any event required for the electrophoretic painting method, for example, the auxiliary electrodes which have to be located at the inside of a car body and its cavities, also to be employed for the electrochemical preliminary treatment. Since these auxiliary means may travel through the apparatus together with each car body, the electro-chemical operations may be accelerated and the periods required for the preliminary treatment may be reduced and the method according to the invention may be carried out more economically also in this respect.

It is therefore an important result which is attained by the present invention and its various features as outlined above that, while the costs of carrying out the new method are no higher or hardly higher than those of the combined spraying and dipping method as previously applied, the end product of the new method is far superior in quality.

A further object of the invention consists in practically eliminating the danger that any residues of the preliminary treatment might settle in the pores of the metal surface so that the liquid of later, more concentrated baths will also not enter these pores. A further improvement of the new method may for this purpose be attained by subjecting the car body prior to the preliminary treatment by the clipping method to a treatment by means of a neutralizing cleansing agent or an anticorrosive agent.

According to another feature of the invention which serves for further improving the quality of the final prodnet, the car bodies or similar articles are sprayed under high pressure with the liquid of a dip bath while being lifted out of this bath or immediately thereafter. Such a spraying which may be carried out, for example, by means of a high-pressure spraying ring above the bath surface and at a high pressure of, for example, about 30 to 50 atm. has the result that any pores of the material of the car body which might still be open will be filled out with the bath liquid, and that any undesirable drying of the surface of the material will also be prevented. Such a spraying of the surfaces of the car bodies or other articles to be treated should be carried out from a short distance. It is therefore advisable to provide a spraying apparatus which complies with the contours of the car bodies or other articles or the spray nozzles of which are adjustable, preferably automatically, so that when a cal body or other article is being lifted out of the bath and passes through the spraying ring, the nozzles will be maintained at the most suitable distance from the surface of the body or article.

According to a further feature of the invention it may be advisable to provide suitable means for positively guiding the car body or other article to be treated while inserting it into the dip tank and/or While lifting it therefrom, for example, by providing guide rails or similar guide elements on the inner wall of the tank for passing a frame along these rails which carries the car body or other article in a vertical position. Such means prevent the car body or the like from swinging back and forth while being inserted into or lifted out of the tank so that it will not hit against the walls of the tank even if the latter closely surrounds the car body or the like. The crosssectional size of the tank, its extension in the direction of travel of the car body or the like, and the amount of material and treating liquid may thus be reduced to a minimum.

Another advantageous feature of the invention consists in the provision of suitable means for moving the car body within the dip tank and preferably for moving it back and forth in a vertical direction so as to wet the car body with the bath liquid as intensively as possible.

Since in many cases a spraying of the car bodies or similar articles with the liquid of the dip tanks at the upper edges of the latter may not suffice and despite such a spraying the danger remains that during the period in which the car body or other article is lifted out of one dip tank, moved to another tank and lowered into the latter, the bath liquid will dry on the car body or the like and thereby cause the detrimental effects on the surfaces of the latter as regards the uniformity and durability of the paint coating, a further feature of the invention consists in spraying the bath liquid upon the car bodies or similar articles when they are lifted out of the tanks so that the spraying is not limited merely to the surface parts which just emerge from the level of the bath.

It is thus advisable to spray the bath liquid upon the car bodies or similar articles when they are lifted fully or substantially from the bath and then upon their entire or substantially entire length and especially upon their upper parts which are lifted out of the bath to the farthest extent so that especially those parts of the surface of the car body or other article which are exposed more than all others to the danger of drying off will be protected from from this danger. In some cases it may not be. necessary to spray the liquid also directly upon the lower parts of the vertically suspended car bodies since these parts will remain lifted out of the baths only for a short time and since the liquid which is sprayed upon the upper parts will run down quickly by gravity to these lower parts. It is, however, advisable to spray the bath liquid additionally upon the car body from positions near the upper edge of the dip tank.

The spraying operation may be interrupted temporarily, if at all, only as long as a car body is moved from a position above one bath to a position above the next following bath of the treatment.

The liquid to be sprayed may consist of the same treating liquid which is contained in the dip tank 'below the car body, for example, the degreasing or paint liquid, but it may also consist of fresh water or any other suitable flushing liquid depending upon the conditions applying to the different baths.

A further feature of the invention consists in providing the hoisting and conveying apparatus itself which is used for lifting and conveying the car bodies or similar articles with spray nozzles for spraying these bodies or other articles after being lifted from the baths. These nozzles are preferably distributed along the height of the hoisting apparatus. Especially, however, and possibly in addition to the spray nozzles which are located near the upper edge of the dip tank, such nozzles are provided adjacent to the upper parts of the vertical suspended car bodies or similar articles, ie the parts which are more remote from the respective baths.

For supplying the liquid to the spray nozzles which are mounted on the hoisting apparatus, a supply or booster tank which is preferably equipped with a pump may be provided on the movable hoisting and conveying apparatus, preferably in such a manner that the liquid to be sprayed is supplied to the booster tank through a relatively stationary line which fills this tank while the latter passes by this line and may be controlled, for example, automatically in response to this passage.

The method according to the invention may be carried out as a so-called rigid method in which the periods of the treatments in the individual treating stages are equal. It is, however, generally of a greater advantage and permits the advantages of the inventive method to be realized as fully as possible if this method is carried out as a nonrigid method in which the periods of the treatments in the individual treating stages may differ from each other. The method may be carried out by means of a closed ringlike apparatus or system or by an open apparatus or system in which the various treating stages or stations follow each other in a straight row.

As already indicated, the present invention may be applied not only for the treatment of car bodies and the like but also for the treatment of other workpieces of similar dimensions which may be dipped in a vertical position similarly as described with respect to car bodies so that the bath liquids will run off as quickly as possible from these workpieces when they are being lifted out of the baths.

The features and advantages of the present invention will become further apparent from the following detailed description thereof which is to be read with reference to the accompanying drawings which diagrammatically illustrate the invention as being applied to a method of painting car bodies or the like. In these drawings:

FIG. 1 shows a diagrammatic side view of the apparatus for carrying out the method according to the invention;

FIG. 2 shows a top view of the apparatus according to FIG. 1;

FIG. 3 shows a diagrammatic horizontal cross section of a dip tank with a car body in a vertical position therein;

FIG. 4 shows a diagrammatic vertical cross section of the dip tank according to FIG. 3; while FIG. 5 shows a diagrammatic vertical cross section of the upper part of a dip tank and a spraying mechanism near the upper end of this tank and above the tank.

In the drawings, the apparatus according to the invention comprises a treating tunnel which contains a plurality of treating chambers or dip tanks 16 and additional treating stages in a straight row behind each other. The car bodies 11 to be treated, some of which are indicated in FIG. 1 at the entry side and the delivery side of the treating tunnel 10 but may in the operation of the apparatus be disposed above the entire row of dip tanks 16 and additional treating stages, are supplied by means of a supply track 12 to an endless conveyer belt 13. Unless this has not already been done previously, each car body is then connected to a supporting frame 20 and moved together with this frame from a horizontal position, as indicated at the left end of FIG. 1, to a vertical position, for example, by pivoting the supporting frame about a horizontal axis or by guide tracks or by means of one of the traveling cranes 14 which are movable along lateral rails 15 and four of which are indicated in 'FIG. 1. The cranes 14 will then draw up the car bodies in their vertical positions so that either their front parts or rear parts hang downwardly. The guide rails 15 extend within a horizontal plane which is located approximate 1y at one half of the height of the car bodies when they have been pulled up to their highest position by the cranes 14.

In this position, the car bodies 11 are lifted off the conveyer belt 13 by the cranes 14 which alternately lower them into the individual dip tanks 16 and lift them out of these tanks and convey them to the following tanks.

The successive treating stages may consist, for example, of a stage A the neutralization bath; B a de greasing and re-degreasing stage; C a flushing stage; D the phosphatising stage; E a cold flushing, re-fiushing and blowing-off stage; P the stage in which auxiliary electrodes are installed; G the electrophoretic prime coating stage; H a flushing and blowing-off stage; I the stage in which the auxiliary electrodes are removed; and K the stage in which after treatments are carried out including drying, cooling, possibly PVC spraying for bottom protection or for producing a sound absorbing layer and subsequent drying, cooling or similar operations. The car bodies travel through this aftertreatment stage, for example, on an endless conveyer belt 17 and near the end of the entire apparatus they are turned by one of the cranes 14 or by a special pivoting mechanism 18 back from their vertical position to a horizontal position and, for example, after being disconnected from their supporting frames, they are conveyed away in a suitable manner by a conveyer belt 19 or the like.

While in the previous description of the series of treating stages it is assumed that the auxiliary electrodes are installed in stage F subsequent to the preliminary treatment, it is, however, also possible to carry out this installation already at the beginning of the preliminary treatment, especially before the phosphatising, so that the auxiliary electrodes which are required for the electrophoresis process may also be employed for the preliminary treatment.

Although it would also be possible to treat the car bodies in one or several stages or stations near the entry of the preliminary treatment zone or near the outlet end of the aftertreatment zone in a horizontal or other position, it is much more advisable for reasons of a greater simplicity of the apparatus, for making it of a shorter length, for facilitating the operations and for obtaining a final product of a high quality if all treatments by bath liquids and those treatments which are associated therewith such as cooling or drying are carried out when the car bodies are suspended in a vertical position. If desired, a special depositing zone may also be included, for example, following the removal of the auxiliary electrodes.

The operations of inserting the individual car bodies into the different tanks or the like, of lifting them therefrom and of conveying them to the next stage or station may all be carried out simultaneously or in accordance with the particular results to be attained, the car bodies may remain for different lengths of time in the individual tanks or be conveyed at different lengths of time from one tank, stage or station to the other, for example, by operating the individual cranes so as to work within certain sections of the entire apparatus. The tanks may all be of the same size or be of different sizes, especially in the conveying direction of the car bodies, or they may be spaced at equal or different distances from each other so that, even though the conveying of the car bodies is basically continuous, it is possible to leave them in some tanks longer than in others without danger that this will interfere with the proper operations of the apparatus.

FIG. 3 shows a cross section of a tank 16 with a car body 11 inserted therein. The car body is removably mounted in any suitable manner on a supporting frame 20, preferably within a plane extending through the center of gravity of the car body, and the supporting frame 20 is movable along vertical guide rails 21 to prevent any oscillations of the frame and car body when being inserted into and lifted out of the tank. FIG. 3 further illustrates the manner in which for carrying out the electrophoretic process individual electrodes 22, which may also be located at the inside of the car body, are distributed around the car body in accordance with the contour of the latter. These electrodes are mounted, for example, on the car body or on the supporting frame and, if desired, they may also be employed in the previous electro-chemical preliminary treatment and will then travel together with the respective car body through the various treating stages and will thus improve and accelerate also the electro-chemical treatment. The electrodes 22 may also be adjustable to different positions, especially in directions extending radially of the axis of the tank.

FIG. 4 shows an axial cross section of one of the cylindrical dip tanks 16. The supporting frame 20 which may be guided in the vertical direction as described with reference to FIG. 3 and holds the car body 11 in a vertical position is suspended on the hoisting mechanism 23 of the traveling crane 14 which is movable along guide rails 15, as illustrated diagrammatically in FIG. 4. Guide rails 15 are located at only a relatively small distance above the upper edge of tank '16 so as to counteract the forces which tend to swing the car body in lateral directions.

FIG. 4 further illustrates that closely above the level of the bath liquid in the tank 16 adjacent to the inner wall of the latter a suitable number of spray nozzles 24 is provided which together form a high-pressure spray ring and are adapted to spray jets of the bath liquid which is also contained in the respective tank 16 under a high pressure upon all sides of the surface of the car body when the latter is being lifted out of the tank. The nozzles 24 may be mounted so as to be adjustable in radial directions relative to the axis of the cylindrical tank 16 so that the individual jets of liquid emerging from the nozzles may be adjusted to the most effective length from the surface of the car body, i.e., so that all jets emerging from the nozzles have substantially the same length. If desired, it is also possible to provide suitable means for controlling the operation of the high-pressure spray nozzles 24 automatically in response to the passage of the car body through the spray ring.

FIG. illustrates an embodiment of the invention in which the hoisting mechanism 114 is provided with rollers 125 so as to be movable along the rails above the dip tank 16 which is provided with spray nozzles 24 closely underneath the level of the upper edge of the tank. A hoist 126 or other suitable elevating mechanism carries each car body 11 and is adapted to lower and immerse the same into the bath 16a which may consist, for example, of a degreasing liquid or a paint, and subsequently to lift the car body again out of the bath 160. During these movements, the car body may be guided in a vertical direction within the tank 16 by a suitable supporting frame similar to the frame as described with reference to FIGS. 3 and 4.

Along the height of the hoisting mechanism 114 and at one, several or all sides thereof a plurality of spray nozzles 127 are provided which are supplied, preferably under a high pressure, with the respective spraying liquid through a system of conduits 128 by means of a pump 129 which may be mounted together with a booster tank 130 on the traveling hoist mechanism 114. This booster tank 130 which only needs to be of relatively small dimensions contains the respective bath liquid 130a which is supplied thereto through a stationary line 131 and control valve means 132 in this line the outlet 133 of which is designed and disposed in such a position that during the longitudinal travel of the hoisting mechanism 114 the booster tank 130 will also travel along underneath the outlet 133. The valve means 132 may be controlled in response to the passage of the booster tank 130 on the hoisting mechanism 114 so that the respective liquid will be supplied from the outlet 133 to the booster tank 130 only as long 8 as the latter is located underneath the outlet 133. The booster tank may for this purpose have an elongated shape extending in the direction of travel of the hoisting mechanism 114. Of course, the booster tank may also be filled while the hoisting mechanism is standing still.

The supply line 131 and/or its outlet 133 may, however, also be designed so as to follow the movement of the booster tank 130 to a certain extent in the direction of travel of the hoisting mechanism 114, for example, by pivotably mounting the upper bent end part of line 131 with the outlet 133 together with or relative to the vertical part of this line and by providing suitable connecting means between the hoisting mechanism and the pivotable part of line 131 so as to pivot the latter during a part of the travel of the hoisting mechanism.

The spraying operation is preferably carried out during the entire lifting movement of the car body from the tank 16 until it reaches approxmately its upper position as shown in FIG, 4, in which the hoisting mechanism 114 starts to move to the next tank 16 or to the next treating stage. The spraying operation usually needs to be stopped only as long as the car bodies are located above and between the tanks into which they are to be inserted. While the Operations of lifting the car bodies and of allowing the bath liquid 16a from dripping off may require a period of, for example, 20 to 30 seconds, the spraying operation may be interrupted, for example, for a period of 5 to 15 seconds.

If different liquids are to be sprayed against the car bodies, for example, a degreasing liquid, a liquid paint and/or fresh water, a separate booster tank 130 may be provided for each of these liquids on the hoisting mechanism 114. Pump 132 or several of such pumps may then be controlled automatically in response to the traveling movement of the hoisting mechanism.

As already described with reference to the nozzles 24, the spraying operation may be carried out under a high pressure. It is, however, also possible to employ a lower pressure as long as the effect will especially be attained that the surfaces of the car bodies will remain moist and the liquid of the respective baths will not dry out on these surfaces while the car bodies are withdrawn from these baths.

Although my invention has been illustrated and described with reference to the preferred embodiments thereof, I wish to have it understood that it is in no way limited to the details of such embodiments but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim is:

1. A method of treating the surface of a sheet metal vehicle body comprising the steps of suspending the body at one end thereof and transporting the body in substantially vertical position over a row of successively arranged dip tanks each containing a treating liquid; moving the body in said vertical position only in vertical direction successively into each of said dip tanks to immerse each body over the whole length thereof in the liquid contained in the respective tank and withdrawing said body only in vertical direction out of the respective tank; and positively guiding the body during movement thereof in vertical direction in and out of the liquid in the respective tank.

2. A method as defined in claim 1, wherein the liquid in at least one of said tanks is a paint, and wherein the liquid in the tanks preceding said one tank in the direction of travel over said tanks serves to pretreat the respective body before being immersed into said paint.

3. A method as defined in claim 2, and including the step of moving the body in vertical direction back and forth in the liquid contained in at least some of the tanks.

4. A method as defined in claim 2, wherein said tanks preceding said one tank contain respectively a degreasing 9 liquid and a liquid for phosphatizing the body immersed therein.

5. A method as defined in claim 4, wherein the tank immediately preceding said one tank contains a flushing liquid.

6. A method as defined in claim 1 and including the step of spraying the body with liquid under pressure, after being at least partly lifted out from the liquid of the respective tank, while maintaining the body in said vertical position, said liquid being taken from the respective tank.

7. A method as defined in claim 1, and including the step of spraying the body while being lifted out from the liquid contained in the respective tank, while maintaining the body in said vertical position.

8. A method as defined in claim 1, and including the step of spraying the body with a flushing liquid after being lifted out of the liquid in the respective tank, while maintaining the body in said vertical position.

9. A method as defined in claim 1, and including the step of spraying each body as it emerges from the liquid in at least one of said tanks from all sides with jets of liquid and arranging said jets with respect to said body so that al of the jets have substantially the same length, while maintaining the body in said vertical position.

10. A method as defined in claim 1, including the step of spraying each body after being lifted out of the liquid in at least one of said tanks with the liquid contained in said tank and spraying said body more intensively at its 10 upper than at its lower parts, while maintaining the body in said vertical position.

11. A method as defined in claim 1, and including the step of spraying each body with liquid in the respective tanks substantially only when the body is above the liquid in the respective tank and interrupting the spraying while the body is moved from the position over one of the dip tanks to a position over the following dip tank, and maintaining the body in said vertical position during spraying and during transportation from one to the following tank.

References Cited UNITED STATES PATENTS 3,011,914 12/1961 Pflug 1171l3 2,919,208 12/1959 Treat 117113 2,728,686 12/1955 Borushko 117113 X 2,598,163 5/1952 Halls 117--113 2,658,008 11/1953 Williams et al. 117113 X OTHER REFERENCES Johnson, Dip Coating, Canadian Paint and Varnish, October 1963, pp. 51-54, 64.

RALPH HUSACK, Primary Examiner US. Cl. X.R. 

